Imaging results are typically used by physicians to diagnose conditions and determine treatments related to a patient's coronary tree, such as blockages in various coronary vessels. For example, if a blockage appears to be serious, the physician may take invasive measures, such as stent insertion or surgery, to relieve the blockage. However, the imaging results alone often do not provide a complete assessment to the physician. In particular, the imaging results do not provide a functional assessment of the patient's coronary tree, which may be valuable to the physician in the diagnosis and subsequent treatment. It is thus desired to have a non-invasive approach for obtaining a functional assessment of the patient's coronary tree.